The present invention relates to a touch sensitive electronic switching circuitry including a C-MOS inverter, for use in electronic wristwatches.
Recently, it has been proposed to provide a touch sensitive electronic switch in an electronic wristwatch because the touch sensitive electronic switch is simple in construction and operation as compared with the conventional mechanical switch such as a stem. Moreover, a switching circuitry for the touch sensitive electronic switch comprising a C-MOS inverter can be incorporated in an integrated circuit constituting a time calculation circuit of the electronic wristwatch.
In such a touch sensitive electronic switch system, a touch sensitive electrode is formed on a preferred position of the casing of the electronic wristwatch, for example, on the front glass window of the electronic wristwatch. Therefore, there is a possibility that a high voltage caused by, for example, a commercial power source may be applied to the touch sensitive electrode. This high voltage will damage the touch sensitive electronic switching circuitry including a C-MOS inverter, when the high voltage is directly applied to the switching circuitry. The touch sensitive electronic switch system described is the subject matter of prior copending application Ser. No. 575,731 filed May 8, 1975 by Sasaki and Maeda which is assigned to the same assignee as the present invention.